A Bose-Einstein condensate, first proposed in 1925 by Albert Einstein based on work done by Satyendra Nath Bose (the same Bose from whom the term boson is derived), is a super-cold state of matter in which almost all of the individual atoms have “condensed” down to the lowest possible quantum energy level.
Steal all their energy by cooling them to a few hundred-millionths of a degree above absolute zero, and atoms will suddenly collapse in on themselves, huddling together like penguins in a blizzard—but with a very important difference.
Under their coats of snow, penguins only look alike. In a Bose-Einstein condensate, the atoms are alike. Exactly alike. There is no known measurement or observation that can tell them apart—not even their locations. In the parlance of quantum mechanics, the wave functions of the atoms have all merged, turning millions of individual atoms into a single entity.
Bose-Einstein condensates are the quantum world made visible to human eyes.
[Source: SLAC National Accelerator Laboratory]